Power tools, as air wrenches and electric wrenches, are used to rapidly turn nuts, bolts, and screws. These tools are not usable to apply twisting forces to the springs of a counterbalancing mechanism of a door, such as an overhead garage door. The counterbalancing mechanisms of overhead garage doors utilize coil springs that are placed under a rotational or torsion force to apply a lifting force to the door. The springs are concentrically positioned about a shaft rotatably mounted on fixed supports. The shaft carries hubs accommodating cables. The cables are attached to the door so that when the hubs are rotated, a lifting force will be applied to the door. The lifting force is transmitted to the hubs via the shaft by the torsion springs. The spring must be twisted to load the spring or place the spring under torsion force. Heretofore, long rods have been used to turn the collar attached to the spring to load the spring. This usually requires two men. A limited amount of force can be applied to the spring since twisting the collar is a manual operation. The procedure requires a considerable amount of time and can be dangerous as the spring is loaded with considerable force. The power tool of the invention obviates the disadvantages of a manual procedure to load the spring of a door counterbalancing mechanism.